1. Field of the Invention
The present invention generally relates to a conveying device and more particularly to a conveying device adapted to move a bolt or similar fastening device along a straight line path over a defined distance and to place a washer, or similar element, onto the shank of the bolt. More particularly, the present invention is related to an apparatus for assembling a washer onto a bolt using a screw type conveyor which moves the bolt in a linear direction while the washer, or similar element, is placed onto the shank of the bolt.
2. Description of the Prior Art
Prior to the present invention, there have been a plethora of devices utilized in the field of assembling bolts and similar fastening devices to washers and similar elements in an expedited fashion and without the need for human intervention. The goals of all of these devices are typically to eliminate the need of human labor when combining two elements, upon a bolt and a washer, in a predictable, fast and efficient manner.
The bolt and washer, for example, are assembled in either one of two states, the first being of the type where the washer freely slides over the fastener or bolt and there is no interference fit between the two. The second is where the washer has an interference fit with the fastener. In each of the above types of fasteners, however, many different apparatus are used to achieve the end result.
One common apparatus uses single or multiple rotating wheels (or discs) to move the bolt (or washer) to a preselected engagement point to meet with the other element with which it is to be combined. In this type of device, the head of the bolt is usually magnetically held by a rotating wheel and the washer is assembled with the head of the bolt in a capture-type arrangement. Some typical examples of the above type of apparatus are Foster, U.S. Pat. No. 4,058,866; Lapohn, U.S. Pat. No. 4,309,787; Stern, U.S. Pat. No. 3,155,993; Pipes, U.S. Pat. No. 3,212,114; Jung et al, U.S. Pat. No. 4,237,605; Jackson, U.S. Pat. No. 4,453,308; Cambiaghi et al, U.S. Pat. No. 4,470,194; and Prutton, U.S. Pat. No. 2,914,781, as well as others. Typically, these types of devices utilize an inclined surface along which the washer and/or bolt are moved in relation to one another in order to achieve the assembly or pick up of the washer on the bolt and the insertion of the washer all the way to the underside of the head of the bolt. These types of devices require moving both the fastener and the washer to the point where they engage each other. This configuration adds unnecessary complexity to the device.
In contrast to the above rotating or disc-like assembly machines, there are several apparatus which utilize an in-line assembly technique. Examples of the above types of apparatus are U.S. Pat. No. 389,648 to Hamilton; U.S. Pat. No. 2,288,620 to Goodhue; U.S. Pat. No. 2,073,096 to Scholz; U.S. Pat. No. 3,103,023 to Zdanis; U.S. Pat. No. 2,333,940 to Kuehlman, and U.S. Pat. No. 3,872,530 to Festerling, as well as other references listed above. In this latter type of device, typically the fastener or bolt is moved in series fashion, one after the other, along a tractor or chain-type device utilized to cause the bolt to move within a defined track. As the bolts move along the track, the shank end of the bolts are caused to come into orientation with washers in a temporary stationary position which are picked up and inserted onto the shank of the bolt. Commonly, a ramp surface of some type is used to move the washer onto and along the shank of the bolt to achieve assembly of the bolts to the washers.
The Hamilton reference, U.S. Pat. No. 389,648, discloses a declining tube with a slot along the underside of the tube. Nails are gravity fed along a slot to a funnel where each nail is deposited through the funnel onto a washer below. U.S. Pat. No. 2,288,620 to Goodhue discloses a link belt carrier for conveying bolts. The bolts are dropped, shank down, onto a carrier. The carrier has clasps adapted to secure the head of the bolt. As the bolts are held by the clasps, the link belt carrier moves around a sprocket, changing the orientation of the bolt stem to an upward position. Washers descend from a trough and are dropped onto the bolt stem. U.S. Pat. No. 3,103,023 to Zdanis discloses an endless conveyor chain similar to the conveyor in Goodhue. However, Zdanis discloses terminal blocks mounted to the conveyor, for carrying the bolts, shank facing upward, along the conveyor path. As the bolt passes under a chute holding washers, a washer is deposited onto the bolt shank. U.S. Pat. No. 3,872,530 to Festerling discloses moving the bolts downward along a conveyor path which passes over a tube containing washers. As the bolt contacts a washer at the tube discharge end, the bolt stem picks up the top washer. As the bolt continues along a downward incline, the washer is pushed up the shank towards the bolt head.
In both the rotating disc type and in-line assembly type apparatus discussed above, typically the bolt or fastener is moved serially along its path by the gravitational force generated through physical contact with adjoining bolts. This force is generally applied to the head of the bolt and thereby is transferred from bolt to bolt. The only exception to the above is when the bolt is picked up by a rotating wheel and is caught within a recess designed to receive the bolt. In this case, the bolt is carried by the wheel in an arcuate or circular path.
Both the rotating disc as well as in-line assembly apparatus have sever limitations when the demand for higher production rates becomes dominant. The centrifugal forces on disc type rotating devices for large bolts cause disturbing forces resulting in misalignments and dislodging the bolt from the discs while the reliance on gravitational forces with associated unknown frictional components results in uneven movements of the components and inability to achieve high production rates resulting in severe derangement of the assembly operation. What is needed, therefore, is a conveying device for assembling a washer to the shank of a bolt wherein higher production rates not previously attainable are achieved by conveying the shank of the bolt in a rapid positive movement mode so that frictional forces or centrifugal forces do not interfere with movement of the fastener such that at these higher production rates, the bolt and washer still arrive at the predefined position for mounting the washer onto the shank of the bolt.
With respect to known prior art devices, nowhere has there been disclosed or taught the idea of using a conveyor for moving the bolt in a straight line wherein the shank of the bolt or other type of fastener is constrained and moved along the thread of a screw conveyor in a straight line manner. Moving one bolt at a time along the thread on a screw to a supply of washers in place ensures adequate separation of components and reliable transfer, resulting in a faster, more reliable assembly process.